diff -r 000000000000 -r 6474c204b198 ipc/glue/SharedMemory.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ipc/glue/SharedMemory.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,99 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <math.h>
+
+#include "nsString.h"
+#include "nsIMemoryReporter.h"
+#include "mozilla/ipc/SharedMemory.h"
+#include "mozilla/Atomics.h"
+
+namespace mozilla {
+namespace ipc {
+
+static Atomic<size_t> gShmemAllocated;
+static Atomic<size_t> gShmemMapped;
+
+class ShmemReporter MOZ_FINAL : public nsIMemoryReporter
+{
+public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+
+  NS_IMETHOD
+  CollectReports(nsIHandleReportCallback* aHandleReport, nsISupports* aData)
+  {
+    nsresult rv;
+    rv = MOZ_COLLECT_REPORT(
+      "shmem-allocated", KIND_OTHER, UNITS_BYTES, gShmemAllocated,
+      "Memory shared with other processes that is accessible (but not "
+      "necessarily mapped).");
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = MOZ_COLLECT_REPORT(
+      "shmem-mapped", KIND_OTHER, UNITS_BYTES, gShmemMapped,
+      "Memory shared with other processes that is mapped into the address "
+      "space.");
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    return NS_OK;
+  }
+};
+
+NS_IMPL_ISUPPORTS(ShmemReporter, nsIMemoryReporter)
+
+SharedMemory::SharedMemory()
+  : mAllocSize(0)
+  , mMappedSize(0)
+{
+  MOZ_COUNT_CTOR(SharedMemory);
+  static Atomic<bool> registered;
+  if (registered.compareExchange(false, true)) {
+    RegisterStrongMemoryReporter(new ShmemReporter());
+  }
+}
+
+/*static*/ size_t
+SharedMemory::PageAlignedSize(size_t aSize)
+{
+  size_t pageSize = SystemPageSize();
+  size_t nPagesNeeded = size_t(ceil(double(aSize) / double(pageSize)));
+  return pageSize * nPagesNeeded;
+}
+
+void
+SharedMemory::Created(size_t aNBytes)
+{
+  mAllocSize = aNBytes;
+  gShmemAllocated += mAllocSize;
+}
+
+void
+SharedMemory::Mapped(size_t aNBytes)
+{
+  mMappedSize = aNBytes;
+  gShmemMapped += mMappedSize;
+}
+
+void
+SharedMemory::Unmapped()
+{
+  NS_ABORT_IF_FALSE(gShmemMapped >= mMappedSize,
+                    "Can't unmap more than mapped");
+  gShmemMapped -= mMappedSize;
+  mMappedSize = 0;
+}
+
+/*static*/ void
+SharedMemory::Destroyed()
+{
+  NS_ABORT_IF_FALSE(gShmemAllocated >= mAllocSize,
+                    "Can't destroy more than allocated");
+  gShmemAllocated -= mAllocSize;
+  mAllocSize = 0;
+}
+
+} // namespace ipc
+} // namespace mozilla